Parabolic trough collectors are parabolically formed solar troughs which concentrate the direct solar radiation onto a so-called focal line in which an absorber tube or a photovoltaic module is attached. The higher the concentration onto the focal point, the better is the energy yield and the efficiency of the device. High concentration can be achieved by parabolic collectors which have a large aperture and high optical precision. Realizing large apertures can further reduce costs by reducing component count per unit energy.
However, when increasing the aperture of a parabolic trough collector, the problem of increased wind loads occurs, which effects that the parabolic mirror moves or swings and that focus deviations occur. For this reason, the aperture in most of the known parabolic trough collectors is limited to a value of 7.51 m, and a complex holding construction is required in order to avoid focus deviations due to wind loads and to achieve optical precision. The holding construction is the main cost driver of such parabolic trough collectors. Currently, considerable efforts are made in order to get a grip on the problem of wind loads on parabolic trough collectors by suitably formed holding devices. Furthermore, it is difficult with the available constructions to generate on site a precise parabolic shape. Costs have been reduced over the last decade by increasing system size, i.e. utilizing larger mirror structures in both width and length, as well as by implementing new and innovative designs. However, further improvements in parabolic troughs have proved difficult, as the industry attempts to achieve high optical precision while minimizing both material and cost in the support structure.
Moreover, in the case of the conventional constructions, any damage thereto results in the fact that possibly the entire collector, namely reflecting components and the holding construction are damaged and have to be replaced.
Finally, shipping of conventional concentrators is expensive and complicated due to the weight and the dimensions of the holding construction and the reflective materials.
The known versions of the parabolic troughs have either an almost exact parabolic shape, but inflexible parameters (parameters are to be understood here as the aperture and the focal length), or slightly flexible parameters, but no exact parabolic shape (e.g. inflatable concentrators). On the other hand, concentrators having slightly flexible parameters (e.g. inflatable concentrators) are usually not robust enough to withstand the adverse weather conditions and do not always withstand the required stress.
An example of such devices from the prior art can be found in US 2010314509 A1 and in WO 2011059062 A1. However, neither ensuring the optical precision or the adjustability of the parameters matters in the two inventions since they do not relate to solar concentrators.